System and method for iron casting to increase casting volumes

ABSTRACT

A system for casting pig iron is provided. The system has a runner, a tundish, and a mold receiving molten iron in a superheated state, and a feed system positioned adjacent to one of the runner, the tundish, and the mold. The feed system contains solid particles having a chemical composition substantially similar to the molten iron, and is positioned to direct a stream of the solid particles the one of the runner, the tundish, and the mold such that the stream of solid particles mixes with the molten iron. A method is also provided. A stream of molten metal is provided in a superheated state during a casting process, and is mixed with a stream of solid particles such that the solid particles at least partially melt with molten metal to increase a volume of the molten metal without substantially changing a chemical composition of the molten metal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application Ser. No. 63/394,020 filed Aug. 1, 2022, the disclosure of which is hereby incorporated in its entirety by reference herein.

TECHNICAL FIELD

Various embodiments relate to a system and a method for increasing an output volume of casted pig iron ingots via additives to molten iron, for example, during a casting process into individual molds.

BACKGROUND

Solid materials may be added to molten metal for alloying purposes to change the chemistry of the molten metal to achieve desired or required chemical specifications. Examples of systems and methods for processing molten metal are provided in PCT Publication No. WO 96/32506, U.S. Pat. Nos. 94,471, 5,817,164, and 3,929,465.

SUMMARY

According to the disclosure, a system for casting pig iron is provided. The system has a runner receiving molten iron in a superheated state, a tundish receiving the superheated molten iron from the runner, a mold positioned beneath the tundish to receive superheated molten iron therefrom, and a feed system positioned adjacent to one of the runner, the tundish, and the mold. The feed system contains solid particles having a chemical composition substantially similar to the molten iron, wherein the feed system is positioned to direct a stream of the solid particles the one of the runner, the tundish, and the mold such that the stream of solid particles mixes with the molten iron.

Also according to the disclosure, a method is provided. A stream of molten metal is provided in a superheated state during a casting process. A stream of solid particles is provided. The solid particles are mixed with the stream of molten metal such that the solid particles at least partially melt with molten metal to increase a volume of the molten metal without substantially changing a chemical composition of the molten metal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic of a casting machine for use with various embodiments according to the present disclosure;

FIG. 2 illustrates a top view schematic of a feed system for use with various embodiments of the present disclosure;

FIG. 3 illustrates a side view schematic of the feed system of FIG. 2 ; and

FIG. 4 illustrates a flow chart of a method for adding solid particles to molten iron in connection with a casting process according to the present disclosure.

DETAILED DESCRIPTION

As required, detailed embodiments of the present disclosure are provided herein; however, it is to be understood that the disclosed embodiments are merely examples and may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present disclosure and invention.

The term “substantially,” “generally,” or “about” may be used herein to describe disclosed or claimed embodiments. The term “substantially” may modify a value or relative characteristic disclosed or claimed in the present disclosure. In such instances, “substantially” may signify that the value or relative characteristic it modifies is within ±0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 10%, 15%, or 20% of the value or relative characteristic.

FIG. 1 illustrates a pig iron casting machine 10 for use with the present disclosure. FIGS. 2-3 illustrate schematics of the feed system 12 or molten iron input to the pig iron casting machine 10 according to an embodiment.

As used herein, pig iron refers to a solid casting 16 of blast furnace molten iron 14. Iron ore, which consists of compounds of iron and oxides, is reduced (the process of removing the presence of oxygen) through the presence of carbon (principally coke) and melted in a blast furnace to produce molten iron, which may then be used to produce commercial iron or made into steel primarily by the removal of the presence of carbon from the molten iron. In various examples, the casting process may form castings 16 by pouring molten iron 14 into individual molds, in contrast to a continuous casting process (also known as strand casting) with a stationary or fixed mold to form a continuous billet or slab.

According to various embodiments, solid particles 18 comprising metal are combined with and added to the molten iron 14 thereby increasing the output volume, or stretching the output volume of pig iron 16. For example, if the volume of molten iron to be casted weighs 100 tons, the weight of the casted pig iron may weigh 115 tons following the introduction of the solid particles 18 based on the addition of the solid particles 18.

In one example, the solid particles 18 are fines. Fines may be provided from metallic processing. In one example, the heat in the molten iron 14 melts the solid particles 18 such that the solid particles 18 are incorporated into the casting and the casting 16 is formed with a substantially homogeneous chemical composition and structure. In another example, the solid particles 18 may be added to the molten iron 14, and the particles 18 may be fused with the surrounding casting 16, for example, if there is insufficient heat to melt and incorporate the particles 18 into the molten iron 14.

According to various examples, the particles 18 have the same chemical composition or substantially the same chemical composition as the molten metal 14. In a further example, the iron fines or solid iron particles 18 have substantially the same chemical composition as the molten iron 14.

According to one example, the molten iron 14 is 92-94% iron (Fe) and 3.5-5% Carbon (C) by weight, and may also contain small percentages or trace amounts of Manganese, Silicon, Sulphur, Phosphorus and/or other trace elements. The solid particles 18 likewise are 92-94% Fe and 3.5-5% C by weight, and may also contain small percentages or trace amounts of Manganese, Silicon, Sulphur, Phosphorus and/or other trace elements.

The solid particles 18 have the same chemical and metallic composition as the molten iron 14, or substantially the same chemical and metallic composition as the molten iron 14. When subjected to the same temperature, the solid particles 18 have a density that is the same or substantially the same as the density of pig iron 14. The solid particles 18 may be provided via a process as described below, and as described further with reference to U.S. Pat. No. 10,478,826 B2 issued Nov. 19, 2019, which is incorporated by reference in its entirety herein and attached hereto. In one example, the solid particles 18 may be generated from solid iron that has been recovered from the slag output of the blast furnace. In other examples, solid particles 18 may be provided by scrap materials such as turnings, steel beebees such as those formed from 98-99% Fe and 1-2% C, raw iron fines, recovered iron-rich fines, or other solid metallic particles with a composition and density that is substantially similar to the pig iron.

The present pig iron disclosure differs from other processes in that the composition of the solid particles 18 is substantially similar to the composition of the molten iron 14, and furthermore, the solid particles 18 are combined with the molten iron metal 14 during the casting process. Conventionally, specified metallic additives may be introduced to molten metals to adjust the metallic or chemical content of the molten metal in creating alloys of the molten metal, where the additives have a different chemical composition than the molten metal, e.g. silicon. Other prior art has added iron ore pellets into molten iron during a casting process; however, the iron ore pellets contain oxides and differ in composition from the molten iron, and the iron ore pellets also do not melt and will not incorporate into the molten iron, such that the final solid product has a heterogeneous structure with the iron ore pellets embedded in the pig iron casting based on the oxide structure of the pellets, and with a varying chemical composition of the iron ore pellets in comparison to the molten metal.

According to one example, a blast furnace produces molten iron 14. The blast furnace uses iron ore, a fuel such as coke, and a flux such as limestone in producing molten iron 14 and slag. In other examples, the molten iron 14 may be provided via another furnace or via another process such as by re-melting pig iron that was previously cast.

The molten iron 14 is poured from the blast furnace typically into a bottle car or other transfer device such as a trough or runner in a liquid superheated state at temperatures above its melting temperature. The iron melting temperature is 2786 degrees Fahrenheit, the molten iron pouring temperature is 2912 degrees Fahrenheit, while the molten iron in its superheated state may be 2912 degrees Fahrenheit or higher when it leaves the blast furnace.

The molten iron 14 travels to a processing system 10 that casts or forms the molten iron into ingots, sows, or castings. The processing system 10 may be a pig iron casting machine as shown schematically in FIG. 1 , or may be another processing system such as a rotary or other machine. For example, molten iron 14 from the bottle car or other source is controllably poured into a receiving receptacle or feed system 12 that feeds the ingot caster line to the pig casting machine.

According to the present disclosure, the solid particles 18 are combined with the molten iron 14 after the molten iron has exited the blast furnace, and also after the molten iron is poured from the transfer device such as a bottle 20 10. The solid particles 18 may be combined with a stream of the molten iron 14 as it is poured from the bottle car 20 to the pig casting machine 10, or as the molten iron 14 is flowing in the feed system 12 to the casting machine. Alternatively or additionally, the solid particles 18 may be added into the molds 26 in the casting line prior to the introduction of the molten iron 14 thereto. 10. In one example, the superheated molten iron 14 flows from the bottle car through a runner 22 and into a tundish 24. The tundish 24 is provided as an open container with an aperture to feed molten iron 14 into a mold 26 and provide a smoother laminar flow while reducing splashing. The tundish 24 may direct the molten iron into a mold 26, such as a mold of a pig iron casting machine 10.

A feed system 12 is provided to direct a stream of solid particles 18 into the stream of molten iron 14 and/or to the casting mold 26 prior to the introduction of the molten iron 14. According to one example, the feed system 12 is positioned adjacent to the runner 22 to direct the stream of solid particles 18 into the runner 22 or trough containing the molten iron. In another example, and as shown, the feed system 12 is positioned adjacent to the tundish 24 to direct the stream of solid particles 18 into the tundish. In yet another example, the feed system 12 is positioned adjacent to a mold 26 to direct the stream of solid particles 18 into the mold 26 upstream of the molten iron 14. In a further example, the feed system 12 is positioned adjacent to another component of the system 10, 12 containing molten iron 14 to direct the stream of solid particles thereto. The feed system 12 receives or contains the solid particles 18 and is positioned to direct a stream of the solid particles 18 into the molten iron in the system component. In one example, the stream of solid particles 18 is directed into the runner 22 or the tundish 24 such that the stream of solid particles 18 mixes and melts into the molten iron 14 after leaving the bottle car 20 and prior to reaching a mold 26. Alternatively or additionally, the stream of solid particles 18 are directed into a mold 26 prior to the introduction of the molten iron 14 such that the solid particles 18 at least partially melts or is incorporated with the molten iron 14, or is fused with the molten iron in the final casting. Introduction of the solid particles 18 directly into the mold may result in a casting with a heterogeneous appearance, as the solid particles 18 may not be entirely melted and incorporated into the molten iron 14 before the material in the mold 26 begins to cool.

In an alternative example, multiple feed systems 12 may be provided such that multiple streams of solid particles 18 are added at different points into the molten iron 14, e.g. with one stream of solid particles 18 directed into a runner 22 and another stream of solid particles 18 directed into a tundish 24, another stream of solid particles 18 is directed into a mold 26, or combinations thereof. Furthermore, when multiple feed systems are used, the feed rate may be the same for each feed system or may vary with the different feed systems based on the location of the feed system, the temperature and volumetric flow rate of the molten iron 14, and the temperature and volumetric flow rate of the associated stream of solid particles 18.

The feed system 12 may be provided with a controller 30 in communication with the feed system 12 to control a feed rate of the stream of solid particles 18, e.g. to provide a specified weight, mass, or volume of solid particles per minute into the stream of molten iron 14, e.g. as a mass flow rate or volumetric flow rate. The solid particle 18 feed rate may be set as a function of at least one of a temperature, and mass or volumetric flow rate of the molten iron 14, the temperature of the particles 18, as well as a location of the feed system 12 within the casting system 10, such that the molten iron 14 is maintained in a superheated state or at or above the pouring temperature after the stream of solid particles 18 is added by the feed system 12. Furthermore, the solid particle feed rate may be set such that the molten iron 14 is maintained in a superheated state or above its pouring temperature until it reaches its final destination, such as a mold 26. The volumetric or mass flow rate and temperature of the molten iron 14 may therefore be used as inputs into the controller 30 to determine the solid particle feed rate, and the controller 30 may use a lookup table or algorithm to determine the appropriate feed rate for the stream of solid particles 18. Temperature sensors may be provided at various locations in the feed system 12 and system 10 to provide inputs to the controller 30 regarding the temperature of the molten iron 14 as well as the temperature of the solid particle 18, as described below.

In one example, the feed system 12 has a volume of solid particles 18 in a bin or the like, or receives solid particles 18 into a hopper 32. A feed mechanism 34 such as an auger feeder may be used to provide the stream of solid particles 18 from the bin or hopper 32 into the molten iron 14 and to control the feed rate of the stream of solid particles 18. The controller 30 may therefore control a rotational rate or speed of the auger feeder 34.

In an alternative example, the feed mechanism 34 may be provided by a vibrating feeder to provide the stream of solid particles 18 from the bin 32 into the molten iron 14 and to control the feed rate of the stream of solid particles 18. The controller 30 may therefore control the amplitude and frequency of the vibrating feeder 34 to control the feed rate of the particles 18. In further examples, the feed mechanism 34 includes both the auger feeder as well as a vibrating mechanism, which may further control the feed rate, reduce clumping, or the like, and also increase the melt rate of the solid particles. Other feed mechanisms 34 may alternatively or additionally be used with the feed system 12 to provide a stream of solid particles 18 into the molten iron, and further control the feed rate. In another example, the stream of solid particles 18 may be added manually to the stream of molten iron in discretized batches, e.g. via a shovel.

The feed system 12 may preheat the solid particles 18 prior to the solid particles 18 mixing with the molten iron 14. The feed system 12 may include a heater 36 such as a torch or other heating device to preheat the solid particles 18. In one example, the stream of solid particles 18 is preheated by positioning and operating a torch countercurrent to the stream of solid particles as they flow towards the molten iron 14. In another example, the bin 32 itself may additionally have a heating element. By preheating the stream of solid particles 18, water content or moisture in the particles is reduced or substantially eliminated, which reduces steam or water flashing when the particles are added to the molten metal 14. Furthermore, preheating the particles 18, prior to being combined with the molten iron 14, the temperature of the superheated molten iron 14 is maintained or is less effected by the addition of the particles 18, which may increase the melt rate and integration of the solid particles 18 into the molten iron 14. With preheating the particles 18, the molten iron 14 is not significantly cooled when the solid particles are added, i.e. the molten iron 14 temperature is not significantly or substantially reduced, and therefore a larger volume or mass of solid particles 18 may be combined with the molten iron 14 while maintaining the molten iron 14 in a superheated state, which allows for further stretching of the molten iron 14 or increased volumetric outputs of the final product 16.

The heater 36 may be connected to and controlled by the controller 30 of the feed system, such that the controller may control the temperature of the preheated solid particles 18 based on the temperature of the molten iron 14, the flow rates of the molten iron 14 and solid particles 18, and the like. For example, the controller 30 may increase the preheating to increase the temperature of the solid particles 18 in response to the molten iron 14 being at or near its pouring temperature. Likewise, the controller 30 may reduce the preheating of the solid particles 18 in response to the molten iron 14 being superheated and substantially above the pouring temperature. In other examples, the heater 36 may be operated manually, or may be at a fixed setting.

In one example, the solid particles 18 are preheated to at least five hundred degrees Fahrenheit by the heater 36. In another example, the solid particles 18 are preheated to at least six hundred degrees Fahrenheit by the heater 36. In a further example, the solid particles 18 are preheated to a temperature within the range of six hundred to eight hundred degrees Fahrenheit by the heater 36. In other examples, other temperature ranges are also contemplated, or the particles 18 may be provided without preheating.

The solid particles 18 may be combined with the molten iron 14 upstream of a mold in a pig casting machine, for example, into a runner 22 or tundish 24 as described above. By adding the solid particles 18 prior to the mold 26, versus placing the solid particles 18 in the mold 26 the melt rate and integration of the solid particles 18 into the molten iron 14 may be increased which may result in part but not limited to increased and improved mixing between the particles 18 and the molten iron 14. Additionally, it may be beneficial to add the particles 18 upstream of the mold as when the solid particles 18 are directly added into the mold 26 they may get caught up or agglomerated with impurities in the molten iron 14 that then forms a skin on the casting 16, and reduces the melting and incorporation of the solid particles into the body of the casting 16. However, as described above, the present disclosure also contemplates that solid particles 18 may be added directly into the mold 26 prior to pouring the molten iron 14 therein.

When the solid particles 18 are combined with the molten iron 14, the superheated molten iron may heat and melt the solid particles, and forms a solution 40 of the two. This solution is then poured into the molds 26. By adding the stream of solid particles 18 into a moving stream of the molten iron 14, melting as well as mixing of the solid particles 18 may be enhanced. Furthermore, adding the solid particles 18 into the tundish 24 may provide enhanced mixing as the flow of the molten iron 14 may be turbulent or may form a vortex in the tundish 24. When particles 18 are directly added to a mold 26, the molten iron 14 may melt or fuse with the particles 18 depending on the temperatures of the molten iron 14 and particles 18 and mold 26, among other factors. The volume of solid particles 18 that is added to the molten iron 14 may be limited however to that which allows the molten iron 14 to maintain a superheated state, and in combination with preheating the particles 18 ameliorates any cooling effect by reducing the amount of energy drawn from the molten iron 14 in melting or fusing with the solid particles allowing for a further increase in the volume of solid particles 18 that can be added as described above.

In one example, the melted solid particles 18 are incorporated and mixed with the molten iron 14 to form a substantially homogeneous molten solution 40 prior to casting the ingots or product 16. As used herein, homogeneous refers to a molten stream, molten volume, or solid that is substantially uniform in chemical and metallic composition and structure throughout. This substantially homogeneous molten solution 40 is then poured in a mold. 26. In the example shown, the substantially homogeneous solution 40 flows from the tundish 24 into a series of casting molds 26 on a moving conveyor system in a pig casting machine 10. The molten metal or solution 40 may be introduced near the “tail” or bottom of the machine 10 and is continuously conveyed to the top of the conveyor.

In another example, the solid particles 18 are placed directly in the mold 26 and are at least partially fused, incorporated and mixed with the molten iron 14, and may form a substantially homogeneous or heterogeneous ingots or product 16. In a further example, solid particles 18 may be mixed with the molten iron 14 upstream of the mold 26, and may additionally be placed in the mold 26 prior to pouring molten iron 14 therein.

The molds 26 containing the combination of the molten iron 14 and solid particles 18, are cooled via a water spray system 42 between the tail and the top. At the end of the casting line, the molds 26 are turned upside down to release and produce a solid casted pig iron product 16. Note that the solution does not cool instantly on the pig casting process 10, and may have a molten center even when leaving the pig casting machine 10 such that the particles 18 may continue to fuse, melt, incorporate, and/or substantially homogenize with the pig iron 14 over an extended time and even while the solution 40 is in the mold.

The solid particles 18, which also may be referred to as metallic fines, are formed as small pieces of iron bearing material, or iron-rich material. In one example, the average size of a particle 18 may be on the order of one millimeters, ten millimeters, or another size. In one example, iron-rich material may refer to particles 18 having an iron content of greater than 80% percent by composition. Furthermore, iron-rich particles 18 may be defined as having a substantially similar chemical and metallic composition and density as pig iron 16

Specifically, when added to the molten iron 14, the solid particles 18 do not substantially change the chemistry of the molten iron 14. The solid particles 18 may be a refined by-product in one example. Therefore, by adding the solid particles 18 to the molten iron 14, a refined by-product is converted into and increases the output volume of a finished pig iron commodity 16 by fusing or melting the solid particles 18 into the molten iron 14 as discussed above. In one example, the melted solid particles 18 provide up to five percent of the volume of a final cast product 16, up to ten percent of the volume of a final cast product 16, up to fifteen percent of a final cast product 16, or more than fifteen percent of a final cast product 16, with the remainder of the volume being provided by the molten iron 14.

As the solid particles 18 have a chemistry that is the same as or substantially similar to the chemistry of the molten iron 14, the limitation on the volume of solid particles 18 that may be added is a function of the superheated temperature of the molten iron 14 versus the latent heat of fusion of the solid particles 18. As the chemistries or compositions of the solid particles 18 and the molten iron 14 are substantially similar, further chemical reactions may not substantially or measurably occur when the solid particles 18 are mixed into the molten iron 14. For example, the solid particles 18 may not substantially undergo a reduction reaction when added to the molten iron 14, and the solution 40 of the particles and molten metal may not substantially undergo a chemical reaction such as a reduction reaction, a reduction oxidation reaction, or an oxidizing reaction as the two are mixed. This does not preclude chemical reactions on a small or limited scale, as there may be trace amounts of materials in the solid particles 18 that do undergo a chemical reaction. Furthermore, as the chemistries of the solid particles 18 and the molten pig iron 14 are substantially similar, mixing of the two does not result in the alloying of the molten iron or pig iron to another alloy, such as a steel alloy, as the final product 16 is a pig iron casting.

In one example, the solid particles 18 comprise iron-rich material from iron-making and steel-making slag fines. In a further example, the solid particles 18 have a density that is the same as or is substantially similar to the molten iron 14 when in solid form and at similar temperatures.

Therefore, a method 50 of producing a volume of solid metal product 16 from a lesser volume of molten iron 14 is achieved by adding solid particles 18 that are substantially similar in chemical and metallic composition to the molten iron 14 in order to stretch the molten iron volume 16. A schematic of the method 50 is illustrated in FIG. 4 . According to the present, non-limiting example, the molten iron 14 is iron produced from iron making in a blast furnace. The solid particles 18 may be iron-rich material from iron-making, or other particles that are substantially similar in chemical composition to the molten iron 14.

A stream of molten iron 14 in a superheated state is provided during a casting process at step 52. A stream of solid particles 18 is added into the stream of molten iron at step 54, and the solid particles melt into the stream of molten iron to form a substantially homogeneous molten solution 40 and thereby increasing the a volume of the molten iron without substantially changing a chemical composition of the molten iron at step 56. Alternatively or additionally, the stream of solid particles 18 may be provided directly into a mold 26 prior to mixing with the molten iron 14 such that the particles fuse, melt, and/or incorporate with the molten iron 14 and form a heterogeneous or homogeneous casting.

Adding the stream of solid particles 18 into the stream of molten iron 14 includes mixing the solid particles 18 into a stream of the molten iron 14, for example, in a runner 22, trough, or tundish 24, or placing the particles 18 into the mold 26 prior to pouring, at step 56. The stream of solid particles may be preheated. The feed rate of the solid particles 18 may be determined or controlled at step 54 such that the stream of molten iron 14 remains in a superheated state or above the pouring temperature after the stream of solid particles have been added, or such that the solution 40 is in a superheated state as it is begin poured into a mold 26. The controller 30 may control the feed rate and preheating of various streams of solid particles at step 54 as a function of the temperature and/or volumetric flow rate of the molten metal 14, the feed rate of the particles 18, and/or as a function of the temperature and/or volumetric flow rate of the solution 40.

The solid particles 18 may be provided at step 54 as iron-rich material from iron-making and steel-making slag fines by subjecting the slag fines to a series of classification steps which progressively sort the slag fines by various physical properties of the material, including magnetism, size, and density, into relatively iron-rich and relatively iron-poor classifications, wherein at least one of the classification steps includes introducing the slag fines as a slurry into a non-compressible fluid fluidized bed separator to separate relatively lower density and relatively higher density constituents of the slag fine particles suspended within the fluidized bed.

The substantially homogeneous molten solution 40 is poured into the mold 26, or the molten iron 14 is poured into a mold 26 containing particles 18. The mold 26 is then cooled to form a casting or final product at step 58. In one example, the mixture of the molten iron 14 and particles 18, which may be a homogeneous solution, may be water cooled while in the mold.

While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the disclosure. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention. 

What is claimed is:
 1. A system for casting pig iron, the system comprising: a runner receiving molten iron in a superheated state; a tundish receiving the superheated molten iron from the runner; a mold positioned beneath the tundish to receive superheated molten iron therefrom; and a feed system positioned adjacent to one of the runner, the tundish, and the mold, the feed system containing solid particles having a chemical composition substantially similar to the molten iron, wherein the feed system is positioned to direct a stream of the solid particles the one of the runner, the tundish, and the mold such that the stream of solid particles mixes with the molten iron.
 2. The system of claim 1 wherein the solid particles comprise iron-rich material from iron-making and steel-making slag fines.
 3. The system of claim 1 further comprising a controller in communication with the feed system to control a feed rate of the stream of solid particles.
 4. The system of claim 3 wherein the feed rate is set to maintain the molten iron in a superheated state after the stream of solid particles is added by the feed system.
 5. The system of claim 1 wherein the mold is supported by a conveyor on a pig iron casting machine.
 6. The system of claim 5 further comprising a water spray system to cool the mold on the conveyor.
 7. The system of claim 1 wherein the feed system comprises an auger feeder.
 8. The system of claim 1 wherein the feed system comprises a vibrating feeder.
 9. The system of claim 1 wherein the feed system comprises a heater to preheat the stream of solid particles.
 10. The system of claim 9 wherein the heater comprises a torch, the torch oriented countercurrent to the stream of the solid particles.
 11. A method comprising: providing a stream of molten metal in a superheated state during a casting process; providing a stream of solid particles; and mixing the solid particles with the stream of molten metal such that the solid particles at least partially melt with molten metal to increase a volume of the molten metal without substantially changing a chemical composition of the molten metal.
 12. The method of claim 11 wherein the molten metal comprises molten iron; and wherein the solid particles have a chemical composition substantially similar to the molten iron.
 13. The method of claim 12 wherein the solid particles comprise iron-rich material from iron-making and steel-making slag fines.
 14. The method of claim 13 further comprising subjecting the slag fines to a series of classification steps which progressively sort the slag fines by various physical properties of the material, including magnetism, size, and density, into relatively iron-rich and relatively iron-poor classifications, wherein at least one of the classification steps includes introducing the slag fines as a slurry into a non-compressible fluid fluidized bed separator to separate relatively lower density and relatively higher density constituents of the slag fine particles suspended within the fluidized bed.
 15. The method of claim 11 further comprising cooling the mixture of particles and molten iron in a mold to form a casting.
 16. The method of claim 15 further comprising water cooling the mold.
 17. The method of claim 11 wherein the stream of molten metal remains in a superheated state after being mixed with the solid particles.
 18. The method of claim 11 further comprising heating the solid particles prior to mixing the solid particles with the stream of molten metal.
 19. The method of claim 18 wherein the solid particles are heated to at least five hundred degrees Fahrenheit.
 20. The method of claim 11 mixing the solid particles with the stream of molten metal further comprises mixing the stream of solid particles into the molten metal in a runner and/or a tundish.
 21. The method of claim 11 wherein mixing the solid particles with the stream of molten metal further comprises providing the stream of solid particles into a mold prior to pouring the stream of molten metal into the mold.
 22. The method of claim 11 wherein the molten metal has a first chemical composition; and wherein the solid particles have a second chemical composition that is substantially similar to the first chemical composition. 